Monitoring Temporal Variation in Glacial Lake Extents in the Upper Indus Basin using Sentinel-1 Synthetic Aperture Radar Data

The number and volume of glacial lakes have substantially increased in the recent decades. As a result, the frequency and intensity of glacial lake outburst floods (GLOFs) is likely to increase. Remotely sensed images have been used to map and monitor glacial lakes; however, the spatiotemporal resolution of most satellite instruments is not fine enough to monitor sudden changes, and cloudy conditions in mountainous areas also limit the use of optical imagery. Synthetic Aperture Radar (SAR) is capable of collecting data under all weather conditions, and Sentinel-1A/1B provide SAR data with a combined revisit time of 6 days. In the current study, the time series of Sentinel-1A/1B SAR imagery from May to October 2021 was used to conduct a high frequency mapping of glacial lakes in the Upper Indus Basin (UIB) via Google Earth Engine's cloud computing. The lower intensity of radar backscatter from flat surfaces of water bodies was exploited to classify the glacial lakes. While most of the glacial lakes showed minimal changes during the study period, several glacial lakes showed high inter-seasonal variations in their extent, including an outburst flood from a glacial lake created by the surging Shishper Glacier. This study demonstrates the capability of Sentinel-1 SAR to quantify dynamics of glacial lakes at a better temporal frequency, helping GLOF predictions and management.